Water for Elephants: “the rules are different”

In the scene where Jacob sits on the grass with the rifle and August comes to talk with him about what he’s just done, Jacob makes the point that technically, he isn’t a veterinarian, to which August replies, “It’s just a piece of paper, and nobody here gives a damn about that. You’re on a show now. The rules are different.”

Are the rules on a show really different? How? Why? In what ways are they exactly the same?